Fire-preventing device for motion-picture-projection machines



l G. J. scHAFFER FIRE PRBVBQTING DEVICE FUR MOTION PICTURE PROJECTIONICHINE2 "Filed June 29. 1922 2 shits-snnz 1 f4 .97 7 la' Nev. 1o, 19'25-G. J. scum-FER FIB; PREVBNTING DEVICE FOR MOTION PICTURE PROJECTIONIACHINES Filed Jung' 29.l 1922 2 Sheets-Shut 2 ifi Patented Nov. 10,1925.

UNITED STATES PATENT GFFICE.

GEORGE J. SCHAFFER, OF LOS ANGELES, CALIFORNIA.

Application tiled June 29, 1922. Serial No. 571,607.

To all whom z't may concern Be it known that I, GEORGE J. SCi-luren, acitizen of the United States, residing at Los Angeles, in the county ofLos Angeles and State of California, have invented new and usefulImprovements in F ire-Preventing Devices for Motion-Picture-ProjectionMachines, of which the following is av specification.

This invention relates to motion picture projectors of the type using ahighly concentrated beam of light for projecting a picture image from atraveling film. This film is usually of highly inflammable character,and an object of the present invention is t provide means forautomatically dowsing or cutting off the beam of light passing throughthe light aperture in the projecting apparatus in the event that thefilm breaks and becomes stationary in the beam of light.

A further object is to provide an automatic dowser of extremely simpleand reliable construction and which may be incorporated with thestandard equipment of the machine with but very slight change andaddition of elements.

Other objects will be made manifest in the following specification of anembodiment of the invention illustrated in the accompanying drawings, inwhich Figure l is a side elevation of a fragment of the projectionapparatus, a part of which is shown in section and with which theinvention is combined.

Fig. 2 is a side elevation and partial section at right angles to theplane of Fig. l.

lFig. 3 is an end view of the lamp housing showing the light shutter inthe open position and showing the shutter controlling mercury pot.

Fig. 4 is a diagrammatic section showing the tiltable mercury pot incircuit closing postion.

Fig. 5 is a similar diagrammatic view showing the mercury pot in thecircuit breaking position.

A portion of a projecting machine housing is indicated at 2, and onewall of this housing is provided with a light aperture 2 in front ofwhich a motion picture film strip F is intermittently advanced duringthe passage of a beam of light through the aperture 2. The film passesover a pair of sprocket wheelsA 4-4 which are spaced somewhat in frontof an opening 2,a in the rear wall of the housing 2 so that a portion ofthe film F forms a loop or bight which may project through the opening2n and is protected and covered by a pocket forming wall or plate 7which may be secured in aclosed position as by a fastening screw 8 atits upper end.

` It is highly desirable to instantly cut oil' a beam of light passingthrough the aperture 2 in the event that the film F should break at apoint below the upper sprocket wheel 4, because in such emergency thefilm F becomes stationary in front of the aperture 2 and will' becomeignited b'y the concentrated beam.

My present invention consists in providing a dowser or cut off device inthe form of a shutter which may consist of a plate 10 secured upon avertically extending rod l1 which projects through the upper end of thecover 7 and holds the dowser l0 normally in an elevated position withrespect to the aperture 2. The rod 11 passes through an aperture 13 inthe ton of the cover 7 and extends therethrough into the loop chamber.On one wall of the cover there is provided bearings le't in which therod is slidably mounted.

Attached to the lower portion of the rod and extending perpendicularlythereto and in substantial parallelism with the upper roller 4 is apresser roller 15 which preferably has flanged ends.

n operation of the device, the presser roller is lifted and a bight B isformed in the film F, and this bight projects into the loop chamber. Thepresser roller l5 is then lowered so as to bear upon the upper portionof the bight. In the event that the film F breaks, the supporting bightunder the roller 15 is therefore eliminated and this permits the rollerl5 withits connected dowser 10 to descend to suchy a position as tobring the dowser into covering position over the light aperture 2.

The dowser is utilized in my present invention as a means forcontrolling the automatic cutting ofi of the beam of light coming fromthe lamp house L of the apparatus so that after the dowser 10 has fallento its effective position over the aperture 2', the beam of light fromthe lamp house L is intercepted and the dowser is prevented from beingheated b v the beam; which heating v would result inthe probableignition of the lm.

The lower end of the dowser is designed to efect-the closing of acircuit for causin vthe closingof a supplementary circuit in w 'ch 1splrovided means for stopping the beam of lig t at the lamp box. l

Th lower end of the Adowser rod 11 is designed to enter a mercury pot inwhich is a bath of mercury 21, the displacement of which, by the entryof the rod 11, raises the level of the mercurg to such degree as toclose -a circuit throng spaced contacts or terminals 22 and 23 providedin the sides of the 'mercury pot 20. The terminals 22--23 haveconnection with aA transforming circuit including the wires 24 having atransformer oil 25 which may be associated with a primary coil in agenerator circuit 26. The low voltage produced in the, circuit 24 isutilized to energize a solenoid 26, the core 27 of which is connected toa lever 28. This leveris attached to a tiltable mercury pot 29.

In the normal position of the mercury -pot 29, a bath of mercury thereinis in covering contact with a vbottom terminal 31'but is out of contactwith a side terminal 32 as seen in Fig. 1.

The terminals 31 and 324 are electrically connected to a circuitincluding wires 33 and including a solenoid `coil 34. In the solenoid isa core 35 attached to a bell crank or lever arm 36. At one end of thebell crank 36 is a shutter or light stop v37 normally in a pendentposition uncovering the tube T arranged at `the, frontv yof the amp boxL.

In operationV of the mechanism when the I film loop breaks in the lilmchamber, the

-dowser 10 is lowered and its rod lplunges into the meruc bath 21 andthis c oses an electrical circult at theop site contacts 22 and 23. Thisclosed circuitl therefore lenergizes the solenoid 26 and the lever arm28 1s pulled down and thus tilts the mercury pot 29. In the tiltingmovement the contacts 31 and 32 swing into'concurrent electrical contactwith the bath of mercury30 as shown in Fi .4. Thereupon the circuit 33is closed, an the solenoid 34 being energized operates the bell crank 36and shifts the light stop or shutter 37 up to covering position over thelighttube T'in which p5 sition it will remain until the operator again'restores the shutter 37 to its vopen position 'aecomo y position shownin Fig. 5 1n which position v V1t will be maintained so long as thesolenoid 26 is energized by the closure of the circuit at the mercurypot 20 in which the lower end of the dowser rod 11 has descended.

The weight of the solenoid parts will hold the shutter 37 u and it isopened by hand.

Various modi cations and changes may be resorted to Within as claimed.

What is claimed is:

1. In a motion picture pro'ecting aplparatus having a light apertureadjacent w ich a motion picture film is designed to pass, means formtercepting avbeam of'light pass- `ing through the light aperture, saidmeans including a vertically slidable rod, a presser member carried bysaid rod adapted to rest upon the'upper portion of a bight continuouslyformed yduring the advance of the picture film, and a plate carried bysaid rod, said presser member,` rod and plate being 'adapted to fall inthe eventv of the breaking the spirit of the invention.

of the film, causing the destruction of said A light aperture.

2. In a motion picture projecting apparatus having a light apertureadjacent which a motion means for lntercepting a beam of vlight passingthrough the light aperture, said means including a vertically slidablerod, a presser roller carried by said rod 'adapted to rest upon theupper portion of a bight continuously forme vduring the advance of thepicture lilm, and a plate carried by said rod, said preer roller, rodand late being ada ted to fall in the event of t e breaking of t e film,causing the destruction of said picture film is designed to pass,

bight whereby said plate may cover said 4 light aperture.

In testimony whereof I havesigned my name to this s ecification. v

EORGE J. SCHAFFER.-

